Gravity waste water collection systems have been used for generations in buildings, including public and private buildings and family residences. The force of gravity carries the waste water from buildings through lateral pipes into a sewer main located at a level lower than the lowest fixture in the building. The main, which serves multiple buildings or residences is usually located in a street or common access way. Over a period of time, the main may become partially blocked due to the growth of roots therein, or due to the presence of other foreign objects. It then becomes over filled in the event of heavy use or increased blockage, causing the waste water to back up through the lateral into the building, usually into the lowest fixture thereof.
There is normally provided a clean-out pipe, to enable laterals extending from the building to the main, to be cleared of any blockage such as tree roots or other foreign matter impeding the flow of wastewater in said lateral. It is also conventional in such systems, to provide a trap at each of the fixtures in the building, to prevent noxious odors from entering the residence from the lateral or main. It is also conventional to provide a vent to carry such odors out of the residence. The vent pipe or stack usually exits the residence through the roof thereof. The clean-out pipe is usually disposed vertically, has interior threads at its upper extremity, and is closed by an exteriorly threaded plug which can be removed by an ordinary wrench.
A number of patents have issued in recent years which propose to solve the back-up problem referred to. For example Rousselet, U.S. Pat. No. 3,603,340, issued in 1971, discloses a drain relief valve wherein the patentee utilizes a "one way" valve or check valve, consisting of a ball and cage to close a drain pipe extending outside of the dwelling. It appears that the valve is not located in a clean-out pipe, like the present invention. Rather it is apparently intended to prevent the backup of wastewater from the outside into the building.
The Westerhoff patent, U.S. Pat. No. 3,805,826 issued ion Apr. 23, 1974 discloses a similar arrangement, except that it contemplates a vertical clean-out pipe connected to a sewer lateral, with a closure mounted at the upper extremity of said clean-out. The Westerhoff closure consists of a relatively loose-fitting slide having a cylindrical shape and having large openings on the side thereof, which is held captive on the outside of the vertical clean-out pipe.
The Robinson patent, U.S. Pat. No. 4,114,641 and the Houston patent U.S. Pat. No. 4,475,571 show relatively more complicated devices to accomplish the same objective as contemplated by the present invention. Both patents disclose the use of a ball flotation element to open the clean-out pipe in a construction which is otherwise very dissimilar to the present invention. Neither patent provides for a closure which can reclose and reseal itself after opening for relief of minor buildup of pressure, or permit the introduction of the conventional tools necessary to remove an obstruction in the lateral.
By far the most relevant patent in this area is that issued to Oberholzer on Dec. 10, 1974, U.S. Pat. No. 3,852,836. It discloses a relief vent which is adapted to be used to close the upper end of a clean-out line, and is shown in the drawings to be disposed flush with the ground level. It utilizes what appears to be a solid member which may be forced out of the opening due to back pressure. However, it has only one gas or odor seal when in the closed position, and that is of such a configuration as to be easily fouled by debris which may be "burped" by the system. Moreover, the solid member is carried in a fitting which can be removed from the clean-out only by means of a specially designed tool not normally carried in the equipment used by a plumber or sewer worker.
The present invention utilizes an assembly to replace the closure normally used in a vertical clean-out pipe, said assembly having a closure which is adapted to be easily forced from the end of the clean-out pipe with minimum pressure. The closure is adapted to be readily inserted by hand and readily removable without special tools, and yet is tamper proof, in the sense that children or vandals would not easily disturb the same. The invention also incorporates a multiple seal to prevent malodorous gases from escaping from the system.